In the past, many expert systems have been developed by establishing a set of rules which defined the individual's area of expertise. Such rule-based systems, however, have had difficulty in addressing the combinatory situations described by a plurality of input variables such as in the medical field. The reason being that a rule-based system needs to address specific circumstances and has been objectionable in areas where the possible combinations are too numerous.
Further, prior rule-based systems have required the expert to work along with a programmer or knowledge engineer in order to implement the system. This has proven to be a time-consuming and expensive process which involves the knowledge engineer translating the expert's decision making process into a fixed program. The amount of time necessary to develop and program a rule-based system, plus the structure of the program that must be written, make these systems difficult to amend in situations where the area of expertise is constantly changing, adapting or improving with new developments.
An additional limitation of the rule-based expert systems is the need for agreement in the particular field of expertise upon the preferred analysis and treatment of the problem in question. In a field such as medicine, for example, this agreement is usually lacking, with many recognized experts having different and sometimes conflicting opinions of the preferred method of analysis and treatment.
In a non-rule based system, Burt U.S. Pat. No. 4,595,982, teaches arranging an internal representation of the expert's logical process and characterizing the situation in terms of a series of intermediate judgments.